Cryogenic refrigerator system and oil separator

ABSTRACT

Provided is an oil separator in which a filter member is arranged between inner and outer punching plates and that includes a filter element configured so that a refrigerant gas that has flowed in from an inlet pipe flows into the filter member through inner through-holes provided in the inner punching plate, and flows outside through outer through-holes provided in the outer punching plate, and a shell that houses the filter element therein and has a bottom portion that collects leak oil that has flowed out of the outer through-holes. An auxiliary flow channel plate for the leak oil is provided in the surface of the outer punching plate, and is configured so that the leak oil is discharged to the bottom portion of the shell through the auxiliary flow channel plate.

INCORPORATION BY REFERENCE

Priority is claimed to Japanese Patent Application No. 2013-026038, filed Feb. 13, 2013, the entire content of which is incorporated herein by reference.

BACKGROUND

1. Technical Field

The invention relates to an oil separator having a filter element for trapping oil included in a refrigerant gas, and a cryogenic refrigerator system to which the oil separator is applied.

2. Description of the Related Art

There are known apparatuses that expand a refrigerant gas boosted by a compressor in a cryogenic refrigerator to generate cooling. Among such compressors, there are compressors that use oil when the refrigerant gas is boosted. Therefore, oil may be included in the boosted refrigerant gas. Thus, the refrigerant gas boosted by the compressor is supplied to a refrigerator after being sent to an oil separator and is subjected to separation of the oil and the refrigerant gas.

SUMMARY

According to an embodiment of the present invention, there is provided a cryogenic refrigerator system including a compressor that boosts a refrigerant gas; an oil separator that separates oil from the boosted refrigerant gas; and a cryogenic refrigerator that expands the refrigerant gas discharged from the oil separator. The oil separator includes a container; an inlet pipe that is arranged at an upper portion of the container and introduces the refrigerant gas; a filter member that is arranged between an inner punching plate having inner through-holes and an outer punching plate having outer through-holes; an outlet pipe that is arranged at the upper portion of the container outside the filter member and allows the refrigerant gas passed through the filter member to be discharged therethrough; a discharge port that is arranged at a lower portion of the container and allows the oil separated by the filter member to be discharged therethrough; and an auxiliary flow channel that is provided outside the outer punching plate and guides the separated oil to the discharge port.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a configuration view illustratively showing a compressor to which an oil separator that is an embodiment of the invention is applied.

FIG. 2 is a partial cross-sectional view of the oil separator that is the embodiment of the invention.

FIGS. 3A and 3B show a filter element internally provided in the oil separator that is the embodiment of the invention; FIG. 3A is a longitudinal sectional view and FIG. 3B is an A-A cross-sectional view in FIG. 3A.

FIG. 4 is a view for describing the flow of leak oil in the oil separator that is the embodiment of the invention.

FIG. 5 is a view for describing the arrangement position of an auxiliary flow channel plate on an outer punching plate.

FIG. 6 is a cross-sectional view showing a filter element internally provided in a first modification example of the oil separator that is the embodiment of the invention.

FIG. 7 is a cross-sectional view showing a filter element internally provided in a second modification example of the oil separator that is the embodiment of the invention.

FIG. 8 is a partial cross-sectional view for describing a third modification example of the oil separator that is the embodiment of the invention.

FIG. 9 is a partial cross-sectional view of a filter element internally provided in an oil separator that is another embodiment of the invention.

FIG. 10 is a cross-sectional enlarged view showing a portion illustrated using arrow B of FIG. 9.

FIG. 11 is a partial cross-sectional view of a filter element internally provided in an oil separator that is a still another embodiment of the invention.

FIGS. 12A and 12B are views showing outer through-holes of the oil separator that are the still another embodiment of the invention; FIG. 12A is a view showing a formation state of the outer through-holes formed within a range shown by arrow UP in FIG. 11, and FIG. 12B is a view showing a formation state of the outer through-holes formed within a range shown by arrow LO in FIG. 11.

DETAILED DESCRIPTION

In a certain oil separator, a filter member is provided within a cell. The oil is separated when the refrigerant gas passes through this filter member. However, if the separated oil is scattered to the downstream side of the filter member, the oil may become mixed-in again to the refrigerant gas.

When the refrigerant gas including oil is supplied to the refrigerator, there is a possibility that the performance of the refrigerator may worsen. Therefore, the improvement in the separative performance of the oil separator is required.

It is desirable to provide an oil separator that can prevent oil that is separated by a filter member from being mixed-in again to a refrigerant gas.

According to an aspect of the invention, oil can be prevented from being mixed-in to a refrigerant gas.

Next, certain embodiments of the invention together with drawings will be described.

FIG. 1 shows a compressor 10 (hereinafter referred to as a compressor) for a cooling storage type refrigerator that is an embodiment of the invention. The compressor 10 is connected to a GM refrigerator 30 by a supply pipe 22 and a return pipe 23.

The compressor 10 boosts a low-pressure refrigerant gas (this refrigerant gas is referred to as a return gas) returned via the return pipe 23 from the GM refrigerator 30 by the compressor body 11, and supplies the boosted return gas again to the GM refrigerator 30 via the supply pipe 22 as a supply gas. The compressor 10 is generally constituted by a compressor body 11, a heat exchanger 12, a high-pressure-side pipe 13, a low-pressure side pipe 14, an oil separator 15, an adsorber 16, the storage tank 17, a bypass mechanism 18, and the like.

The return gas returned from the GM refrigerator 30 first flows into the storage tank 17 via the return pipe 23. The function of the storage tank 17 is to remove pulsation included in the return gas.

The return gas the pulsation of which is removed in the storage tank 17 is led out to the low-pressure side pipe 14. The low-pressure side pipe 14 is connected to the compressor body 11. Hence, the return gas the pulsation of which is removed in the storage tank 17 is supplied to the compressor body 11.

The compressor body 11 is, for example, a scrolling or a rotary pump, and fulfills the function of boosting the return gas (the refrigerant gas that is boosted in the compressor body 11 is referred to as the supply gas). The compressor body 11 delivers the boosted supply gas to a high-pressure-side pipe 13A. In addition, when the supply gas is boosted in the compressor body 11, the supply gas may be delivered to the high-pressure-side pipe 13A in a state where oil within the compressor body 11 is slightly mixed-in to the supply gas.

Additionally, the compressor body 11 is configured to be cooled by oil. For this reason, an oil cooling pipe 33 that allows oil to be circulated therethrough is connected to an oil heat-exchange section 26 that constitutes the heat exchanger 12. Additionally, the oil cooling pipe 33 is provided with an orifice 32 that controls the flow rate of oil that flows therethrough.

The heat exchanger 12 is configured so that cooling water is circulated through a cooling water pipe 25, and has the oil heat-exchange section 26 that performs the cooling processing of the oil that flows through the oil cooling pipe 33, and a refrigerant gas heat-exchange section 27 that cools the supply gas. The oil that flows through the oil cooling pipe 33 is heat-exchanged and cooled in the oil heat-exchange section 26, and the supply gas that flows through the high-pressure-side pipe 13A is heat-exchanged and cooled in the refrigerant gas heat-exchange section 27.

The supply gas boosted in the compressor body 11 and cooled in the refrigerant gas heat-exchange section 27 is supplied to the oil separator 15 via the high-pressure-side pipe 13A. In the oil separator 15, the oil included in the supply gas is separated from the refrigerant gas, and impurities and dust included in the oil are also removed. In addition, for convenience, a detailed configuration of the oil separator 15 will be described below.

The supply gas of which the oil is removed in the oil separator 15 is sent to the adsorber 16 via a high-pressure-side pipe 13B. The adsorber 16 fulfills the function of removing, particularly, an evaporated oil component included in the supply gas. After the evaporated oil component of the supply gas is removed in the adsorber 16, the supply gas is supplied to the GM refrigerator 30 via the supply pipe 22.

The bypass mechanism 18 is constituted by a bypass pipe 19, a high-pressure-side pressure detecting device 20, and a bypass valve 21. The bypass pipe 19 is a pipe that allows a high-pressure side, to which the supply gas of the compressor 10 flows, to communicate with a low-pressure side to which the return gas flows. The high-pressure-side pressure detecting device 20 detects the pressure of the supply gas within the high-pressure-side pipe 13A. The bypass valve 21 is an electric valve gear that opens and closes the bypass pipe 19. Although the bypass valve 21 is a normally-closed valve, the bypass valve is controlled by the high-pressure-side pressure detecting device 20.

Specifically, when the high-pressure-side pressure detecting device 20 has detected that the pressure (that is, the pressure within the high-pressure-side pipe 13A) of the supply gas from the compressor body 11 to the oil separator 15 becomes equal to or higher than a predetermined pressure, the bypass valve 21 is driven and opened by the high-pressure-side pressure detecting device 20. This prevents the supply gas of the predetermined pressure or higher to be supplied to the refrigerator 30.

Subsequently, the oil separator 15 will be described.

FIG. 2 is a cross-sectional view showing the oil separator 15 that is the embodiment of the invention, and FIG. 3 is a schematic configuration view showing a filter element 36A internally provided in the oil separator 15. The oil separator 15 is generally constituted by a shell 35 and the filter element 36A.

In addition, the left half of the filter element 36A with respect to a centerline is shown in section in FIG. 2, and the right half of the filter element 36A with respect to the centerline is shown in section in FIG. 3.

Subsequently, the oil separator 15 will be described.

The oil separator 15 has the shell 35 and the filter element 36A.

The shell 35 is constituted by a cylindrical portion 35A, an upper flange 35B, a bottom portion 35C, and the like. The cylindrical portion 35A is formed in a hollow tubular shape. The bottom portion 35C is fixed to and is airtightly closed by a lower end portion of the cylindrical portion 35A by welding or the like. Additionally, the upper flange 35B is fixed to an upper end portion of the cylindrical portion 35A by welding or the like, and the upper end portion is also airtightly closed.

A high-pressure gas introduction pipe 15A, a high-pressure gas lead-out pipe 15B, and an oil returning pipe 15C are arranged at the upper flange 35B. The high-pressure gas introduction pipe 15A is connected to the high-pressure-side pipe 13A. Hence, the supply gas boosted in the compressor body 11 is introduced into an inner space formed inside an inner punching plate 41.

The high-pressure gas lead-out pipe 15B is connected to the high-pressure-side pipe 13B. The high-pressure-side pipe 13B is a pipe that connects the oil separator 15 and the adsorber 16. Additionally, an oil return port is connected to an upper end portion of the oil returning pipe 15C. Additionally, an introduction opening 56 provided at a lower end portion of the oil returning pipe 15C opens in the vicinity of a bottom portion of the oil separator 15.

The oil return port is connected to the oil return pipe 24. The oil return pipe 24 has a high-pressure side connected to the oil separator 15 and a low-pressure side connected to the low-pressure side pipe 14. Additionally, a filter 43 that removes the dust included in the oil separated by the oil separator 15 and an orifice 31 that controls the return amount of oil are provided in the middle of the oil return pipe 24.

The filter element 36A is constituted by the high-pressure gas introduction pipe 15A, a filter member 37, an upper lid body 38, a lower lid body 39, and an outer punching plate 40A, the inner punching plate 41, and the like.

The filter member 37 has, for example, the structure in which glass wool is wound around the core of the inner punching plate 41 and the outer punching plate 40A is arranged at an outermost peripheral portion of the filter member. Hence, the filter member 37 is configured so as to be arranged between the inner punching plate 41 and the outer punching plate 40A. The upper lid body 38 is fixed to an upper end portion of the filter member 37 by using an adhesive (not shown), and the lower lid body 39 is fixed to a lower end portion of the filter member by using an adhesive.

As a result, the filter member 37, the upper lid body 38, the lower lid body 39, the outer punching plate 40A, and the inner punching plate 41 have an integral configuration. The filter member 37 is fixed to the high-pressure gas introduction pipe 15A by welding the upper lid body 38 to the high-pressure gas introduction pipe 15A.

Both the outer punching plate 40A arranged outside the filter member 37 and the inner punching plate 41 arranged inside the filter member 37 have a tubular shape. Additionally, outer through-holes 50A are formed in the outer punching plate 40A, and inner through-holes 51 are formed in the inner punching plate 41. The respective through-holes 50A and 51 has a circular shape, and the supply gas (refrigerant gas) introduced into the filter element 36A from the high-pressure gas introduction pipe 15A is introduced into the filter member 37 through the inner through-holes 51 formed in the inner punching plate 41.

Then, when the supply gas advances inside the filter member 37, the oil included in the supply gas is removed by the filter member 37. Additionally, the supply gas the oil of which is removed by the filter member 37 is discharged to the outside (the interior of the shell 35) of the filter member 37 through the outer through-holes 50A of the outer punching plate 40A.

Incidentally, when the supply gas advances inside the filter member 37 from the inner punching plate 41 toward the outer punching plate 40A, the oil included in the supply gas is removed by the filter member 37. In this case, when the supply gas includes a large amount of oil, the filter member 37 is not able to hold oil. As a result, a portion of oil may leak to a surface 44 of the outer punching plate 40A through the outer through-holes 50A (hereinafter, the oil leaked through the outer through-holes 50A is referred to as leak oil 60).

The leak oil 60 is dropped on the bottom portion 35C of the shell 35 from the filter element 36A and is reserved at a lower portion of the shell 35. Then, the leak oil 60 reserved at the lower portion of the shell 35 is returned to the compressor body 11 via the oil returning pipe 15C, the oil return pipe 24, and the low-pressure side pipe 14.

The distribution of oil within the filter member 37 is shown by pear skin in FIG. 3A. The oil trapped in the filter member 37 moves downward due to gravity. For this reason, as shown in FIG. 3A, although the distribution of the oil within the filter member 37 is little at an upper portion of the filter member, the oil increases gradually toward a lower portion of the filter member. For this reason, the leak oil 60 leaked through the outer through-holes 50A of the outer punching plate 40A also increases compared to the leak oil 60 leaked through an upper portion of the outer punching plate 40A.

When the leak oil 60 leaked on the surface of the outer punching plate 40A through the outer through-holes 50A flows into other outer through-holes 50A, the leak oil 60 forms an oil film so as to block the outer through-holes 50A. Since refrigerant gas flows out from the inside toward the outside through the outer through-holes 50A, the oil film of the leak oil 60 will be splashed and scattered by this refrigerant gas if the oil film of the leak oil 60 is formed in the outer through-holes 50A (this phenomenon is referred to as bubbling).

When this bubbling has occurred, the leak oil 60 may again be mixed-in to the supply gas the oil of which is removed by the filter member 37.

Here, the oil separator 15 related to an embodiment provides an auxiliary flow channel plate 45A on the surface of the outer punching plate 40A. The auxiliary flow channel plate 45A is a thin-plate-shaped member having a rectangular shape (an elongated rectangular shape in the longitudinal direction of the outer punching plate 40A). The auxiliary flow channel plate 45A is fixed to an outer peripheral surface of the outer punching plate 40A by a well-known fixing method, such as welding.

The auxiliary flow channel plate 45A is arranged so as to extend along the longitudinal direction (up-and-down direction in FIGS. 2 and 3A)] of the outer punching plate 40A. The auxiliary flow channel plate 45A may be formed over the entire length of the outer punching plate 40A in the longitudinal direction. Additionally, a plurality of (twelve in the present embodiment) the auxiliary flow channel plates 45A are also received, and the respective auxiliary flow channel plate 45A may be arranged so as to extend radially from the surface of the outer punching plate 40A toward the outside, as shown in FIG. 3B.

Additionally, the arrangement positions of the auxiliary flow channel plates 45A on the outer punching plate 40A do not need to exclude the arrangement positions of the outer through-holes 50A. As shown in FIG. 5, the auxiliary flow channel plates 45A may be arranged so as to straddle the outer through-holes 50A. In this case, the auxiliary flow channel plates 45A may be arranged so as to straddle only one outer through-hole 50A and or may be arranged so as to straddle two or more outer through-holes 50A.

As described above, since the auxiliary flow channel plates 45A are simple plates having a rectangular shape, the auxiliary flow channel plates can be easily manufactured. Additionally, the auxiliary flow channel plates 45A can be fixed to the outer punching plate 40A by using a well-known technique, such as welding. Hence, the auxiliary flow channel plates 45A can be easily arranged at the outer punching plate 40A at low costs.

Next, the behavior of the leak oil 60 in the filter element 36A where the auxiliary flow channel plates 45A are arranged will be described.

FIG. 4 is a cross-sectional enlarged view illustrating the vicinities of the positions of the outer punching plate 40A and the auxiliary flow channel plate 45A where the outer through-holes 50A are formed. In this drawing, the left side in the drawing is the inner side of the filter element 36A, and the right side is the outer side of the filter element 36A.

As mentioned above, when the supply gas includes a large amount of oil, the filter member 37 no longer holds the oil, and a portion of the oil leaks to the surface 44 of the outer punching plate 40A through the outer through-holes 50A as the leak oil 60.

As mentioned above, if the auxiliary flow channel plate 45A is not provided, since the leak oil 60 flows downward toward the surface of the outer punching plate 40A, the leak oil may re-flow back to the outer through-holes 50A and thus, the bubbling may occur.

However, the oil separator 15 related to the present embodiment protrudes from the outer surface of the outer punching plate 40A, and is provided so that the auxiliary flow channel plate 45A extends in the longitudinal direction of the auxiliary flow channel plate 45A, that is, in the flow direction of the leak oil 60. Additionally, the auxiliary flow channel plate 45A is provided in the vicinities of the outer through-holes 50A, and the portion of the auxiliary flow channel plate 45A that is formed over the outer through-holes 50A is also present.

Accordingly, a flow channel, along which the leak oil 60 that has flowed out of the outer through-holes 50A adheres to the auxiliary flow channel plate 45A as shown in FIG. 4 and then flows downward on the surface of the auxiliary flow channel plate 45A, is formed. That is, in the present embodiment, a flow channel, along which the leak oil 60 that has flowed out of the outer through-holes 50A is stripped from the surface of the outer punching plate 40A and flows through the auxiliary flow channel plate 45A, is formed. For this reason, the amount of the leak oil 60 that flows on the surface of the outer punching plate 40A decreases. As a result, the leak oil can be prevented from flowing again into the outer through-holes 50A.

In this way, in the filter element 36A related to the present embodiment, the leak oil 60 that has flowed out of the outer through-holes 50A is prevented from flowing again into the other outer through-holes 50. Therefore, the occurrence of bubbling can be suppressed, and accordingly, the leak oil 60 can be prevented from being again mixed-in to the supply gas.

Additionally, a dropping portion 47 may be provided at a lower end portion of the auxiliary flow channel plate 45A. In the embodiment, the dropping portion 47 is formed so as to become gradually narrow from the inner side to the outer side. The dropping portion 47 has a triangular shape when viewed from a side surface.

By providing the dropping portion 47, the leak oil 60 that has flowed on the auxiliary flow channel plate 45A is dropped on the bottom portion 35C of the shell 35 from a tip portion (pointed portion) of the dropping portion 47 at a position apart from the surface of the auxiliary flow channel plate 45A. Hence, due to the dropping portion 47, the leak oil 60 on the auxiliary flow channel plate 45A is also returned again to the surface of the outer punching plate 40A. As a result, the leak oil 60 can be prevented from being again mixed-in to the supply gas.

Next, modification examples of the oil separator 15 related to the above-mentioned embodiment will be described. FIGS. 6 to 8 show first to the third modification examples of the oil separator 15 related to the embodiment.

In addition, since the respective modification examples have features in the filter element of the oil separator 15, only the filter element is shown in the respective drawings and illustration of the shell 35 is omitted. Additionally, in FIGS. 6 to 8, components corresponding to those of the first embodiment shown in FIGS. 1 to 5 will be described by the same reference numerals, and the description thereof will be omitted.

FIG. 6 shows a filter element 36B provided at an oil separator that is a first modification example.

In the oil separator related to the present modification example, the auxiliary flow channel plate 45B is arranged at least below a middle position of the outer punching plate 40A in the longitudinal direction. That is, if the length of the auxiliary flow channel plate 45B in the longitudinal direction is defined as L1 and the length of the outer punching plate 40A in the longitudinal direction is defined as L2, L1<L2 is established, and the auxiliary flow channel plate is provided within a range from the lower end portion of the outer punching plate 40A to a dimension (L2/2).

As previously described using FIG. 3A, the distribution of the oil within the filter member 37 increases toward the lower portion of the filter member, and the leak oil 60 leaked through the outer through-holes 50A of the outer punching plate 40A becomes heavier at a lower portion of the outer punching plate 40A than at an upper portion of the outer punching plate.

For this reason, the present embodiment has a configuration in which the auxiliary flow channel plate 45B is arranged only below the middle position, in the longitudinal direction, of the outer punching plate 40A where the amount of leak of the leak oil 60 through the outer through-holes 50A is larger. According to the configuration of the present modification example, stripping processing of the leak oil 60 from the outer punching plate 40A can be efficiently performed, and miniaturization of the auxiliary flow channel plate 45B can be achieved.

FIG. 7 shows a filter element 36C provided at an oil separator that is a second modification example. In the present modification example, the shape of the auxiliary flow channel plate 45C is a triangular shape that becomes wider downward.

As mentioned above, the amount of the leak oil 60 leaked through the outer through-holes 50A of the outer punching plate 40A is larger at the lower portion of the outer punching plate. Hence, the amount of the leak oil 60 that flows on the outer through-holes 50A increases toward the lower portion.

In contrast, in the present modification example, the area of the lower portion is made larger than that of the upper portion by forming the auxiliary flow channel plate 45C in a triangular shape that becomes wider downward. By adopting this configuration, it is possible to make a large amount of leak oil 60 flow at the lower portion of the auxiliary flow channel plate 45C. Hence, at the lower portion of the auxiliary flow channel plate 45C holding a large amount of leak oil 60, the leak oil 60 can be prevented from returning to the outer punching plate 40A and flowing into the outer through-holes 50A.

FIG. 8 is a cross-sectional enlarged view illustrating the vicinities of the outer through-holes 50A of a filter element provided at an oil separator that is a third modification example. In the present modification example, guide grooves 48 are formed in the auxiliary flow channel plate 45C.

As shown in FIG. 8, the guide grooves 48 are formed so as to extend obliquely downward from positions near the outer through-holes 50A formed in the outer punching plate 40A. By providing the guide grooves 48 in the auxiliary flow channel plate 45D, the leak oil 60 that has flowed out of the outer through-holes 50A and adheres to the auxiliary flow channel plate 45D flows into the guide grooves 48.

The leak oil 60 that has flowed into the guide grooves 48 flows along the shape of the guide grooves 48. Hence, the leak oil 60 is guided by the guide grooves 48 and flows in a direction away out from the surface of the outer punching plate 40A. As a result, even in the present modification example, the leak oil 60 that has flowed out of the outer through-holes 50A can be prevented from flowing again into the outer punching plate 40A and the outer through-holes 50A. Hence, the leak oil 60 can be prevented from being again mixed-in to the supply gas the oil of which is removed by the filter member 37.

In addition, in the present modification example, the extending direction of the guide grooves 48 is set so as to become about 45° downward with respect to the horizontal direction, but this angle can be appropriately changed. That is, as the angle of the guide grooves 48 with respect to the horizontal direction becomes larger, the speed at which the leak oil 60 flows through the guide grooves 48 becomes faster.

Additionally, although the shape of the guide grooves 48 is a long elliptical shape in the present modification example, the shape of the guide grooves 48 is not limited to this. For example, the shape of the guide grooves may be a nonlinear shape, such as an L-shape, and the width, length, and depth of the guide grooves can also be appropriately changed. It is possible to appropriately control the flow speed (the amount of flows) and flowing position of the leak oil 60 on the auxiliary flow channel plate 45D depending on the angle with respect to the horizontal direction, width, length, depth, shape, and the like. This can also prevent the leak oil 60 that has flowed out of the outer through-holes 50A from flowing again into the outer punching plate 40A and the outer through-holes 50A.

Next, an oil separator that is a still another embodiment of the invention will be described. FIGS. 9 and 10 are views for describing the oil separator that is the still another embodiment.

In addition, since this embodiment also has a feature in a filter element 36D of the oil separator, only the filter element 36D is shown in the respective drawings, and the illustration of the shell 35 is omitted. Additionally, even in FIGS. 9 and 10, components corresponding to those of the first embodiment shown in FIGS. 1 to 5 will be described by the same reference numerals, and the description thereof will be omitted.

The oil separator related to this embodiment is characterized by providing the filter element 36D with a collar portion 49. A plurality of (six in the present embodiment) the collar portions 49 are provided on the surface of the outer punching plate 40A. Additionally, the respective collar portions 49 are provided in parallel.

Each collar portion 49 is formed so as to surround the surface of the outer punching plate 40A, and the shape of the collar portion in a cross-section extends further downward than the horizontal shape (see a cross-sectional portion on the left of the centerline of FIG. 9). Accordingly, it can be said that the collar portions 49 have an umbrella shape.

Additionally, each collar portion 49 is formed so as to cover at least one outer through-hole 50A. FIG. 10 shows an enlarged portion illustrated using arrow B of FIG. 9. As shown in this drawing, in the present embodiment, the collar portion 49 is configured to cover one outer through-hole 50A.

In the oil separator related to the present embodiment, the leak oil 60 that has flowed out of the outer through-holes 50A, as shown in FIG. 10, flows along upper surfaces of the collar portions 49 that extend obliquely downward, and is dropped at the bottom portion 35C of the shell 35 from lower end portions of the collar portions 49.

Hence, even in the present embodiment, the leak oil 60, that has flowed out of the outer through-holes 50A, flows on the collar portions 49, is stripped from the surface of the outer punching plate 40A, and separates from the surface of the outer punching plate 40A, as it flows on the collar portions 49. Accordingly, even in the present embodiment, the leak oil 60 that has flowed out of the outer through-holes 50A can be prevented from flowing again into the outer punching plate 40A and the outer through-holes 50A. Hence, the leak oil 60 can be prevented from being again mixed-in to the supply gas the oil of which is removed by the filter member 37.

In addition, the angle (shown by arrow θ in FIG. 10) of the collar portions 49 with respect to the surface of the outer punching plate 40A can be set to a range of 0°≦θ≦90°. Although the flow speed of the leak oil 60 on the collar portions 49 becomes slow by making this inclination angle θ small, the leak oil 60 can be separated from the surface of the outer punching plate 40A by a short length. Additionally, when the inclination angle θ is made small, the flow speed of the leak oil 60 on the collar portions 49 becomes fast. However, it is necessary to make the collar portions 49 extend long in order to separate the leak oil 60 from the surface of the outer punching plate 40A.

Additionally, in the embodiment shown in FIGS. 9 and 10, the outer punching plate 40A is provided with the plurality of collar portions 49. However, it is also possible to adopt a configuration in which a collar portion is formed in a spiral shape and the leak oil 60 that flows out of the outer through-holes 50A is stripped from the surface of the outer punching plate 40A by one collar portion as the result of the configuration.

Next, an oil separator that is a still another embodiment of the invention will be described. FIGS. 11 and 12 are views for describing an oil separator that is a third embodiment. Additionally, FIG. 12A shows the enlarged surface of the outer punching plate 40B of a region illustrated using arrow UP of FIG. 11, and FIG. 12B shows the enlarged surface of the outer punching plate 40B of a region illustrated using arrow LO of FIG. 11.

In addition, since this embodiment also has a feature in a filter element 36E of the oil separator, only the filter element 36E is shown in the respective drawings, and the illustration of the shell 35 is omitted. Additionally, even in FIGS. 11 and 12, components corresponding to those of the first embodiment shown in FIGS. 1 to 5 will be described by the same reference numerals, and the description thereof will be omitted.

In the oil separator related to the present embodiment, the open area ratio (the ratio of the total hole area of the outer through-holes to the total surface area of the outer punching plate 40B) of the outer through-holes 50B and 50C formed in the outer punching plate 40B of the filter element 36E is changed at the upper portion and lower portion of the outer punching plate 40B. Specifically, in the oil separator related to the present embodiment, the open area ratio of the outer through-holes 50C arranged below (the region shown by arrow LO in FIG. 11) a middle position in the longitudinal direction of the outer punching plate 40A is set to be smaller than the open area ratio of the outer through-holes 50B arranged above (the region shown by arrow UP in FIG. 11) the middle position.

In the present embodiment, the individual outer through-holes 50B and the individual outer through-holes 50C have the same diameter (the same area). Accordingly, the number of the formed outer through-holes 50C arranged in the region LO (shown in FIG. 12B) below the middle position is smaller than the number of the formed outer through-holes 50B arranged in the region UP (shown in FIG. 12A) above the middle position.

Accordingly, when a flow channel along which the leak oil 60 in the surface of the outer punching plate 40B flows is taken into consideration, the flow channel area becomes narrow in the region UP above the middle position shown in FIG. 12A. On the other hand, the flow channel area becomes wide in the region LO below the middle position shown in FIG. 12B.

As mentioned above, the amount of oil included in the filter member 37 is not uniform at upper and lower positions, is smaller in the region UP above the middle position, and is larger in the region UP below the middle position. For this reason, in the region UP above the middle position of the outer punching plate 40B, the outflow amount of the supply gas is large but the outflow amount of the leak oil 60 is small. On the contrary, in the region LO below the middle position of the outer punching plate 40B, the outflow amount of the leak oil 60 is large but the outflow amount of the supply gas is small.

Hence, the supply gas the oil of which is removed by the filter member 37 efficiently flows out of the outer punching plate 40B into the shell 35 through the multiple outer through-holes 50B formed in the region UP above the middle position.

On the other hand, as mentioned above, since the oil removed by the filter member 37 flows downward through the filter member 37, the leak oil 60 that flows out of the outer through-holes 50C in the lower region LO increases. However, as shown in FIG. 12B, in the lower region LO, the distance between adjacent outer through-holes 50C is long and the flow channel of the leak oil 60 is ensured. For this reason, the leak oil 60 that has flowed out of the outer through-holes 50C flows out downward without flowing again into the other outer through-holes 50C (the flow of the leak oil 60 is shown by arrow in FIG. 12B).

Hence, the leak oil 60 that has flowed out of the outer through-holes 50C can be prevented from flowing again into the other outer through-holes 50C. Therefore, the leak oil 60 can be prevented from being again mixed-in to the supply gas the oil of which is removed by the filter member 37. Additionally, since the supply gas flows outside the filter element 36E in the upper region UP with a large open area ratio, the outflow resistance of supply gas can be made small, and efficient gas-liquid separation can be performed.

In addition, the above-described embodiment has a configuration in which the open area ratio of the lower region LO with respect to the upper region UP is increased by making the diameters of the respective outer through-holes 50B and 50C be the same dimension and changing the number of the formed outer through-holes 50B in the upper region UP and the number of arranged outer through-holes 50C in the lower region LO.

However, the open area ratio of lower region LO with respect to the upper region UP can also be increased by setting the numbers of formed through-holes in the upper region UP and the lower region LO equal to each other and changing the diameters of the outer through-holes 50B and the outer through-holes 50C different from each other.

That is, the open area ratio of the lower region LO with respect to the upper region UP can be increased evenly by making the diameter of the outer through-holes 50C arranged in the lower region LO smaller than the diameter of the outer through-holes 50B arranged in the upper region UP.

Additionally, the above-described embodiment has a configuration in which the outer punching plate 40B are divided into the upper region UP and the lower region LO at the middle position, and the open area ratio is changed in the upper region UP and the lower region LO. However, a configuration may be adopted in which the number and the diameter of the outer through-holes are changed so that the open area ratio of the outer through-holes increase gradually from the upper end portion of the outer punching plate 40B toward the lower end portion thereof.

Although the preferable embodiment of the invention has been described above in detail, the invention is not limited to the above-described specific embodiment, and various alterations and changes can be made within the scope of the invention described in the claims. 

What is claimed is:
 1. A cryogenic refrigerator system comprising: a compressor that boosts a refrigerant gas; an oil separator that separates oil from the boosted refrigerant gas; and a cryogenic refrigerator that expands the refrigerant gas discharged from the oil separator, wherein the oil separator includes: a container; an inlet pipe that is arranged at an upper portion of the container and introduces the refrigerant gas; a filter member that is arranged between an inner punching plate having inner through-holes and an outer punching plate having outer through-holes; an outlet pipe that is arranged at the upper portion of the container outside the filter member and allows the refrigerant gas passed through the filter member to be discharged therethrough; a discharge port that is arranged at a lower portion of the container and allows oil separated by the filter member to be discharged therethrough; and an auxiliary flow channel that is provided outside the outer punching plate and guides the separated oil to the discharge port.
 2. The cryogenic refrigerator system according to claim 1, wherein the auxiliary flow channel is arranged at least below a middle position of the outer punching plate in an up-and-down direction.
 3. The cryogenic refrigerator system according to claim 1, wherein the auxiliary flow channel has a length such that the channel straddles at least two or more outer through-holes in the up-and-down direction.
 4. The cryogenic refrigerator system according to claim 1, wherein the auxiliary flow channel has a groove portion that guides the separated oil to a bottom portion in a surface thereof.
 5. The cryogenic refrigerator according to claim 1, wherein the auxiliary flow channel is a plate-shaped member that extends in an up-and-down direction.
 6. The cryogenic refrigerator system according to claim 1, wherein the auxiliary flow channel includes a collar portion that extends vertically and downwardly with respect to the surface of the outer punching plate, and the separated oil is dropped to the discharge port from a position apart from the surface of the outer punching plate.
 7. The cryogenic refrigerator system according to claim 1, wherein the open area ratio of the outer through-holes arranged below a middle position of the outer punching plate in an up-and-down direction is smaller than the open area ratio of the outer through-holes arranged above the middle position.
 8. The cryogenic refrigerator system according to claim 1, wherein the number of the formed outer through-holes arranged below a middle position of the outer punching plate in a longitudinal direction is smaller than the number of the formed outer through-holes arranged above the middle position.
 9. The cryogenic refrigerator system according to claim 1, wherein the diameter of the outer through-holes arranged below a middle position of the outer punching plate in a longitudinal direction is smaller than the diameter of the outer through-holes arranged above the middle position.
 10. An oil separator used for a cryogenic refrigerator system, the oil separator comprising: a container; an inlet pipe that is arranged at an upper portion of the container and introduces a refrigerant gas; a filter member that is arranged between an inner punching plate and an outer punching plate; an outlet pipe that is arranged at the upper portion of the container outside the filter member and allows the refrigerant gas passed through the filter member to be discharged therethrough; a discharge port that is arranged at a lower portion of the container and allows oil separated by the filter member to be discharged therethrough; and an auxiliary flow channel that is provided outside the outer punching plate and guides the separated oil to the discharge port. 